The Tommotian Age, named after the
mollusc" Tommotia", which began approx. 530 million years ago is an early part of the Cambrianperiod and lasted for only about 3 million years.
climateduring the Tommotian was mild; there was no glaciation. Most of North America lay in warm southern tropical and temperate latitudes, which supported the growth of extensive shallow-water archaeocyathidreefs all through the Lower Cambrian. Siberia, which also supported abundant reefs, was a separate continent due east of North America. Baltica - what is now Scandinavia, eastern Europe, and European Russia - lay to the south. Most of the rest of the continents were joined in a supercontinent known as proto- Gondwana. What is now China and east Asia was fragmented at the time. Western Europe was also in pieces, with most of the pieces lying northwest of what is now the north African coastline.
The Tommotian saw the rise of diversified
metazoans with skeletons, small shelly fauna, the first archaeocyathids, primitive molluscs - monoplacophorans, Lapworthella, and inarticulate brachiopods. Archaeocyaths are sponges with a simple morphology. Their calcareous skeleton consists of an inner and an outer wall that are variably connected. The small shelly faunaconsists of various calcareous(also some silica, some calcium phosphate) fossils some 1-5 mm long. They represented a variety of organisms: sponges, molluscs, annelids, lobopods, and other forms that do not seem to belong to any recent phylum. Many of these organisms were recognized either as of unknown affinity or as representatives or groups that became extinct before the end of the Cambrian. The most primitive stage is marked by characteristic elements, such as anabaritids, tommotiids, and hyolithellids, also known as the "Tommotian fauna". This period had the first major radiations of animals.
The origin of the many kinds of skeletons during this time was a major evolutionary development. The rapid evolution of a variety of external skeletons was probably in response to the evolution of advanced predators.
*http://employees.oneonta.edu/ebertjr/Ediacarans,%20Small%20Shells,%20Phanerozoic.ppt Powerpoint presentation with images
Wikimedia Foundation. 2010.
Look at other dictionaries:
Small shelly fauna — The small shelly fauna or small shelly fossils, abbreviated to SSF, are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian period. They… … Wikipedia
Halkieria — Taxobox name = Halkieria fossil range = fossil range|533|511|Lower to Middle Cambrian image title = Halkieria evangelista from the Lower Cambrian Sirius Passet, North Greenland regnum = Animalia phylum = ?Mollusca unranked ordo = Halwaxiida… … Wikipedia
Tommotia — Taxobox name = Tommotia fossil range = Early Cambrian image caption = Tommotia admiranda regnum = Animalia phylum = incertae sedis (possibly stem Brachiopoda) classis = incertae sedis ordo = Mitrosagophora genus = Tommotia Tommotia is a small… … Wikipedia
Small-Shelly-Fauna — Bei der Small Shelly Fauna (SSF) – oft fälschlich auch als „Tommotium Fauna“ bezeichnet – handelt es sich um mineralisierte Fossilien, oftmals nur einige Millimeter groß, die von den letzten Stufen des Ediacarium bis hin zum Ende der frühen… … Deutsch Wikipedia
Archaeocyatha — Taxobox name = Archaeocyatha fossil range = Early Late Cambrian domain = Eukaryota unranked regnum = Opisthokonta regnum = Animalia subregnum = Parazoa phylum = Porifera? (sponges) unranked classis = Archaeocyatha 1 – Gap ( intervallum ) *2 –… … Wikipedia
Cambrian Period — Oldest time division of the Paleozoic Era. During the Cambrian, 543–490 million years ago, there were widespread seas and several scattered landmasses. The largest continent was Gondwana. The average climate was probably warmer than today, with… … Universalium
Cambrian — For other uses, see Cambrian (disambiguation). Cambrian Period 542–488.3 million years ago … Wikipedia
Early Cambrian — The Early Cambrian (also known as the Caerfai, Waucoban, or Georgian) is the first of three geological epochs of the Cambrian period. It spans the time between 542 ± 0.3 Ma and 513 ± 2 Ma (million years ago). The Cambrian explosion of complex… … Wikipedia
Geologic time scale — This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga. Other… … Wikipedia
Cambrian explosion — The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex animals around Ma|530, as evidenced by the fossil record. [http://www.ucmp.berkeley.edu/cambrian/camb.html The Cambrian Period] ]… … Wikipedia